Structured Interrupts

All interrupts contain three fields:

• message,
• data, and
• kind.

We've already seen how you can pass the message and data as the first and second parameters to the interrupt() function. To pass in the kind, use the structured interrupt format.

return interrupt foo::write(
  "Are you sure you want to write to this file?",
  { filename: filename }
)

In this example, foo::write is the kind of the interrupt. You can set this to anything you want. Interrupts in the standard library are prefixed with std::.

What are kinds good for? They're useful if you want specific responses for different kinds of interrupts in handlers:

def deleteEmail(numEmails: number) {
  return interrupt foo::deleteEmail(
    "Are you sure you want to delete ${numEmails} emails!!!",
    { numEmails: numEmails }
  )
  print("deleting ${numEmails} emails! DO DO DO!")
}

handle {
  deleteEmail(aMillion)
} with (data) {
  // Reject any interrupt for deleting email.
  // Approve all other interrupts.
  if (data.kind == "foo::deleteEmail") {
    return reject()
  }
  return approve()
}

Kinds give you a way to programmatically identify and handle different interrupts in handler blocks. If you don't specify the kind, it is automatically set to "unknown".

Kinds are also useful if you want to write policies that apply to specific kinds of interrupts.